1. Field of the Invention
This invention relates to a rotary magnetic recording-reproducing apparatus, and more particularly to a rotary-magnetic recording-reproducing apparatus for reproducing information recorded in a rotary magnetic recording medium such as a magnetic disc. Especially, this invention relates a rotary magnetic recording-reproducing appartus wherein information recorded on tracks formed concentrically on the magnetic disc is reproduced with a tracking servo being applied thereto.
2. Description of the Prior Art
Recently, there has been developed an electronic still camera system wherein an image pickup device such as a solid state image sensing device or an image pickup tube is combined with a recording device using an inexpensive magnetic disc as a recording medium and yet having a comparatively high memory capacity, a subject is stillphotographed purely electronically and recorded into a rotating magnetic disc, and the reproduction of an image is carried out by a television, a printer or the like, which are provided separately.
However, the recording medium used in the above-described magnetic recording, particularly, the magnetic disc tends to cause a tracking failure due to anisotropy, eccentricity, thermal expansion and the like. Consequently, there is such a disadvantage that a track adjacent a predetermined track is scanned during reproduction, whereby a crosstalk is caused.
To obviate this disadvantage, a tracking signal is recorded with a tracking servo being applied during recording of information, and during reproduction the tracking servo is applied by use of the tracking singnal. However, it is impracticable to provide a tracking servo mechanism requiring highly accurate control on a recording apparatus being compact in size and light in weight, such as a camera.
Firstly, there is such a method that, as the recording system, a guard band system or an FM azimuth system is adopted and the tracking failure occurring to some extent during reproduction is compensated in such a manner that a reproducing head does not scan the adjacent track and, even if the reproducing head scans, the reproducing head does not pick up a signal of the adjacent track.
Along with the above, a so-called peak searching system is used, wherein during recording a recording head is transferred at a predetermined track pitch by a stepping motor without the tracking servo being applied, during reproduction enveloped of output signals of respective tracks are detected, the optimal track is discriminated from a position of peak and the tracking servo is applied.
In the rotary magnetic recording used in the electronic still camera system, 50 tracks are recorded on a disc having a diameter as small as about 50 mm at a track pitch of about 100 .mu.m, i.e. a track width of about 50.about.60 .mu.m and a guard band width of about 50.about.40 .mu.m for example. In the recording or reproducing apparatus, this magnetic disc rotated at a constant speed of 3000 rpm for example, and image signals are recorcded or reproduced at a field or frame speed.
The above-described compact magnetic disc being thin and having the small diameter is normally housed in a mold package (hereinafter referred to as a "disc pack") made of plastics, etc. for handling. Namely, each disc pack is loaded in a loading position of a recording or reproducing apparatus, whereby the magnetic disc, housed in the disc pack, is rotatably driven for recording or reproduction.
Now, in the rotary magnetic recording-reproducing appratus, it is necessary to display a track number upon completion of the tracking on each of the tracks. In such a case as described above, the handling of the tracks matters when there is a dropout track or an unrecorded track. In the rotary magnetic recording-reproducing apparatus, if the dropout of a signal occurs in a track of the magnetic disc for example, the track may be skipped and the succeeding perfect track may be recorded. In other words, in the reproducing apparatus wherein a track number is discriminated simply on the basis of the transferred distance of the reproducing head, even a defective track, in which no image signal is recorded, is discriminated as if an effective track and the track number thereof is displayed. In consequence, inconvenience may occur in the operation of such a reproducing apparatus that an image of a desirable frame number is to be rapidly selected and displayed. Namely, in the case of users, it suffices to number-display the recorded tracks successively. Reproduced images can be displayed on the display screen in accordance with the number displays, thus enabling to avoid giving a feeling of disorder to the users.
However, if all of the handlings are made by such an addressing as described above, namely, skipping the defective tracks, the following disadvantage will be presented. Namely, in the reproducing apparatus of the type wherein the reproduction is performed with the unrecorded track or tracks being skipped, such a disadvantage may be presented that, when it is desired to know what is recorded in a certain track irrespective of the quality of the record to some extent or when it is desired to know as to whether a certain track is judged as an unrecorded track and skipped because of a defectively recorded state of something or of no recording being made entirely, the track cannot be observed.